Carboxylic acids are organic compounds of the form R-COOH (double bond to one O and single bond to a hydroxyl (OH) group). They're acids because the carboxyl group is capable of dissociating to give R-COO- and H+ (a proton). R is a parent group. The simplest R is hydrogen (H), giving methanoic acid, aka formic acid, found in ant and bee venom and stinging nettle poison. Then you have a methly group (CH3) as R, giving ethanoic acid aka acetic acid, aka vinegar. You can keep going on with these single bonded alkyl chains to give simple carboxylic acids. Or you can have more complex Rs, like benzene rings (giving benzenecarboxylic acid, aka benzoic acid), or atoms other than carbon or hydrogen.

Amino acids are important special cases, where the R contains an amine -NH2 group, making the compound have both a basic and acidic part (you can read up on how that makes the overall compound behave at different pH values, look up a zwitterion).

Relevance to the economy ? Well, since they are utterly relevant to life itself, I'd say the economic relevance is a given. You can look up vinegar in the food industry, benzoic acid in various chemical processes and for a slightly unconventional approach, discuss the economic impact of treating people for bee stings (formic acid) and the need for refrigeration of butter so it won't spoil to give butyric acid.